The invention relates to a flameproofed resilient block polymer comprising polymerized units of at least one vinylaromatic monomer and at least one diene monomer with at least one flameproofing agent B), a process for the preparation and the use for the production of moldings.
Thermoplastic polymer materials treated with expandable graphite, which is also known as exfoliated graphite, as a flameproofing agent are known. For example, according to WO 03/046071 A1, expandable graphite is used in polystyrene (PS) or high impact polystyrene (HIPS). In addition, according to this document, a halogen-containing compound is required in amounts of from 2 to 11%, calculated as halogen, as a further flameproofing component. However, it is desirable as far as possible substantially to avoid the use of halogen-containing flameproofing agents.
Thermoplastics which are flameproofed without halogen and comprise expandable graphite and a phosphorus compound as flameproofing components are discussed in WO 00/034367 and WO 00/34342. Molding materials based on styrene polymers flameproofed in this manner are, however, worthy of improvement with regard to their dripping behavior in a fire.
KR1996-0001006 discloses flameproofed polystyrene, the flameproofing components comprising expandable graphite, a phosphorus compound and Teflon. The mean particle size of the expandable graphite is 5 μm. The Teflon added as an antidrip agent is used in amounts of from 1 to 5 percent by weight.
Resilient block copolymers likewise flameproofed with exfoliated graphite, a phosphorus compound and a fluorinated polymer are discussed in the European patent applications EP 07112183.4 and EP 07116636.7, the polymer components of the first-mentioned document being acrylonitrile-butadiene-styrene copolymers (ABS) and acrylate-styrene-acrylonitrile copolymers (ASA) and those of the second-mentioned document being PS and HIPS.
Often, in the case of thermoplastic molding materials which are rendered flame-retardant with expandable graphite, it is difficult firstly to achieve sufficient flame retardance and secondly nevertheless to maintain sufficiently good mechanical properties.
In numerous applications in the electrical and electronic area (computers and office equipment, etc.), such as insulations, in the automotive interior area and in the construction sector, flame-retardant materials are prescribed. For corrosion and health reasons, halogen-free solutions for flameproofing are desired. In order to achieve sufficient halogen-free flameproofing at all, combinations of additives, such as exfoliating graphite (intumescent), Teflon dispersions (to prevent dripping), phosphate salts of melamine, red phosphorus (free radical scavenger in the flame), metal hydroxides (water donor), etc. have to be used. The disadvantage of such additives used in considerable proportions by weight is a usually considerable decline in the toughness.